Using Photoelectron Spectroscopy and Quantum Mechanics to Determine d-Band Energies of Metals for Catalytic Applications

The valence band structures (VBS) of eight transition metals (Fe, Co, Ni, Cu, Pd, Ag, Pt, Au) were investigated by photoelectron spectroscopy (PES) using He I, He II, and monochromatized Al K alpha excitation. The influence of final states, photoionization cross-section, and adsorption of residual gas molecules in an ultrahigh vacuum environment are discussed in terms of their impact on the VBS. We find that VBSs recorded with monochromatized Al K alpha radiation are most closely comparable to the ground state density of states (DOS) derived from quantum mechanics calculations. We use the Al K alpha excited PES measurements to correct the energy scale of the calculated ground state DOS to approximate the true ground state d-band structure. Finally, we use this data to test the d-band center model commonly used to predict the electronic-property/catalytic-activity.relationship of metals We find that a simple continuous dependence of activity on d-band center position is not supported by our results (both experimentally and computationally).